Some gravure engravers of the past included one or more engraving heads which have a diamond stylus mounted on an arm projecting from a torsionally oscillated actuator shaft. A sine wave driving signal is applied to a pair of opposed electromagnets to rotate the actuator shaft through a maximum arc of approximately 0.25.degree. at a maximum frequency of between 3 to 5 KHz. When torsionally oscillated, the actuator shaft moves the diamond stylus into and out of a copper-plated surface of a gravure cylinder to form or cut holes or cells in the cylinder surface. Gravure cylinders range in size from 6 inches to 15 feet in length, and 4 to 26 inches in diameter. Typically, 20,000 to 50,000 cells per square inch are engraved on a gravure cylinder.
Present engraving heads can produce about 3200 cells per second on the surface of a gravure cylinder when operating at about 3.2 KHz. Thus, the time required to completely engrave a cylinder is typically on the order of hours. The operating frequency for present engraving heads is limited by the mass of the magnetic material used to actuate the stylus. The engraving heads shown and disclosed in U.S. Pat. Nos. 3,964,382 and 4,357,633 show examples of engraving heads and stylus drivers of the type used in the past.
What is needed, therefore, is an engraving head which can move a diamond stylus into and out of a copper-plated surface of a gravure cylinder at a frequency rate greater than present engraving heads, thereby facilitating reducing the time required to engrave a gravure cylinder.